Many important crops, such as corn and soybeans, are planted in rows of substantial and uniform spacing, as distinguished from crops which are planted by a broadcast method or other crops which are planted in rows so narrow that upon emergence and growth, the crop effectively covers the surface of the soil and is neither cultivated nor harvested in rows. Implements for planting, cultivating and fertilizing row crops are thus typically designed so that the working tools, whether they engage the ground (as in planters and cultivators) or not (as in sprayers), are laterally spaced along a frame or toolbar at the same spacing as the crop rows are spaced. Depending on the type of implement, there may be one or more ground-engaging tools associated with each crop row; and the tools for each row are normally mounted on a separate device called a "row unit." A row unit, if it includes ground-engaging tools, normally has its own support wheels and is mounted to the toolbar by means of a four-bar linkage or equivalent which allows each row unit to move vertically to adjust to the contour of the ground independently of the other row units on the same toolbar. For those row units which do have ground-engaging tools, there typically is a need to gauge the depth of working. This is normally done by supporting the row unit with support wheels which are referred to as depth gauge wheels or, simply, gauge wheels.
Thus, gauge wheels are used to support the row units of a drawn agricultural implement to establish the operating depth of a ground-engaging tool carried by the row unit. The gauge wheels are disposed on and travel over the surface of the soil. The ground-engaging tool operates at a depth lower than the ground-engaging surface of the gauge wheels by a predetermined distance. One task typically performed by row units for cultivators, planters, fertilizer applicators and other implements designed for operation in high residue fields involves the cutting of crop residue, vines and weeds (generally referred to as "residue") between adjacent crop rows to permit the cultivator sweep, in that case, to cut growing weeds without being plugged up with residue, or to part the residue for furrow formation in the case of a planter. The present invention is disclosed principally in the context of a cultivator row unit in FIGS. 1-10. It is also shown in a planter row unit in FIGS. 11-13; but persons skilled in the art will recognize that the invention is equally well suited for use with fertilizer applicators and other agricultural implements designed for use in environments having high surface residue and is not necessarily limited to row units. For example, it may be adapted to fertilizer applicators, either particulate or anhydrous ammonia.
There are two different approaches currently practiced for gauging coulter depth in implements of the type with which the present invention is concerned. One type uses a single wheel placed directly in front of the coulter. This approach has the advantages that a wheel of larger diameter may be used to provide better flotation (sometimes referred to as having a larger "rolling diameter"), and, for the same flotation (or weight-bearing capacity without substantially compacting the soil), the width of the tire may be narrower. A narrower width has the advantage that the wheel is less likely to contact adjacent tender crop or pass over crop root, either of which may cause damage. Further, a narrow front profile provides a better fit in the swales between rows in ridge farming.
The disadvantage of the single forward wheel system is that the cutting action of the coulter is less effective than a two-wheel system in which the wheels are placed rearward to straddle the coulter. An object of the two-wheel system is to place the tires adjacent the location at which the coulter enters the soil and begins to cut the residue. The wheels hold and tension the residue while the coulter cuts it. Typical two-wheel systems are seen in U.S. Pat. No. 2,440,174 (Howard) and U.S. Pat. No. 4,834,189 (Peterson et al.).
In the two-wheel system, the wheels must be placed in a diverging relation by mounting the wheels on separate axles. That is, the wheels are closer together toward the front and below the horizontal plane passing through the center of the wheels (referred to as the lower front quadrant). From that point, the wheels diverge upwardly and rearwardly in order to provide space to receive the coulter blade. In other words, the wheels have intersecting axes of rotation. In the two-wheel approach, there are important design trade-offs or compromises which must be made.
First, the larger the diameter of the wheels, the greater will be the tendency of the wheels to interfere with the hub mounting the coulter. Further, increasing the angle of divergence of the wheels (to provide space for the coulter blade) for a given wheel diameter, desirably permits the coulter to be moved forward which provides a cutting advantage, but at the same time, the amount of divergence, the diameter of the wheels and the width of the wheels all contribute to the overall maximum operating width of the wheels. The maximum operating width, on the other hand, is limited by the spacing of crop on adjacent rows. Thus, as a practical matter, in the two-wheel system, the width of the wheels is reduced (resulting in reduced flotation); the diameter of the wheels is reduced (also reducing flotation) to avoid interference with the coulter hub and permit the coulter blade to be positioned further forward; and the coulter is not located as far forward as desired (to reduce the angle of divergence, and thus the maximum width of the wheels).
Nevertheless, the performance of the two-wheel system is generally preferred over the one-wheel system, and it is generally practiced in cultivator row units.
To summarize the disadvantages with existing two-wheel systems, if an unskilled operator drives the tractor, there might be some crop damage due to the maximum width of the gauge wheel arrangement and the tight tolerances with crop row spacing. If the field is a "no-till" or heavy residue field, there might be insufficient cutting of stalks, vines and tougher, less-decayed residue because the gauge wheels are not located at the exact location where the coulter enters the soil and begins cutting. It is at this location that the gauge wheels should ideally be placed because that is where the wheels can best hold (and even tension if the wheels are slightly toed inwardly) the residue as the coulter cuts it. Further, as accessories are added to the row unit, the weight increases; and the wheels, due to their smaller diameter, have a tendency to compact the soil and form a groove or furrow in soft or wet soil. Water then drains and collects in the grooves, drawing the water away from the crop root, where it is desired. In the prior art, the gauge wheels are separated in the lower front quadrant. The space between them permits residue to pass between the wheels and be gathered and dragged by the assembly. Dragging the residue with the cultivator also tends to plug the trailing cultivator sweep, thus reducing its effectiveness.
The present invention addresses these limitations of the prior art by providing a gauge wheel arrangement particularly adapted for use in a cultivator row unit (but equally useful, for example, in a planter operating in high residue and other implements) wherein the row units are mounted to a toolbar for independent vertical motion, as conventionally done. This permits each row unit to adjust to uneven ground contour, but requires depth gauging at each row unit.
According to the invention, a pair of side-by-side gauge wheels are mounted on intersecting axes, inclined (or toed) inwardly toward each other such that they engage each other at a forward location below a plane passing through the center of the wheels and above the location at which the wheels engage the soil (i.e., the lower front quadrant of the wheels). The axes extend slightly upwardly and rearwardly proceeding from the outside to the center of the unit. The gauge wheels, thus inclined, are placed close together to engage each other as described and to diverge as one proceeds up and to the rear. Further, the wheels are preferably semi-pneumatic tires, not inflated, to provide a large footprint for improved row unit support. The spacing between the diverging gauge wheels at the rear permits a trailing coulter to be placed in a more forward position to improve cutting of crop residue, vines and weeds because, even with gauge wheels of larger diameter (e.g., 12 inches or larger), the wheels engage and secure the residue at the location where the coulter enters the ground to cut the residue.
As indicated, the wheels are arranged to contact each other at a location forward and above the point at which the gauge wheels contact the ground. For example, when viewed from the left side (i.e., the left side of one looking in the direction of forward travel), the gauge wheels engage the soil slightly before and aft of the six o'clock position, and their inner edges firmly contact each other over an arc defined by an angle of approximately 30-60.degree. centered at approximately midway between the seven-eight o'clock position, that is, in the lower front quadrant of the wheels. By firmly contacting each other, it is meant that the wheels are forced together during assembly so that the semi-pneumatic tires deform slightly to form a solid profile or wall. This enables the combined wheels, even though comparatively narrow individually, to roll over mounds of residue. It also prevents crop leaves from entering between the wheels and being pinched off or otherwise damaged. The wheels diverge from one another as one proceeds from the contact area through the point at which the axes of rotation of the gauge wheels intersect, and then to the one-two o'clock position, where the divergence of the gauge wheel tires is at its maximum to receive the coulter mounting arm and hub.
Further, the diameter of the gauge wheels may be made larger (increased, for example, from 12 inches to 16 inches in the case of an 18 inches diameter coulter). The larger diameter gauge wheels have greater flotation which permits the gauge wheels to have a narrower width for the same flotation or weight-carrying ability, as the smaller diameter wheels. This divergence or rear opening of the gauge wheels combined with the narrower width of the gauge wheels permits the gauge wheels to be placed more toward the rear relative to the coulter (conversely, as stated, the coulter may be moved forward). Moreover, because the wheels are narrower, the gauge wheels may be spaced further apart to straddle the coulter hub, and still present a substantially narrower overall width than the wider, smaller diameter wheels of prior units. This results in a lesser tendency to interfere with the crop, or to form furrows because of the large diameter and cooperative effect of placing the two wheels together where they begin to engage the ground.
Further, the wedge-shaped, solid front profile for the inventive gauge wheel arrangement permits the unit to pass between crop rows while brushing crop to the side, as opposed to running over the crop when the unit gets too close to the crop. And the diverging arrangement of the wheels tensions residue trapped beneath both wheels as the wheels pass over the residue. This makes the cutting more effective.